Conducting an Internal Corporate Investigation: Procedures, Privilege, and Best Practices
Lesley Brovner & Mark Peters
September 8, 2026
Once an internal corporate investigation is authorized, the next phase is execution. How the investigation is conducted—what documents are reviewed, who is interviewed, how data is preserved, and how privilege is protected—can determine whether the investigation withstands regulatory scrutiny or collapses under challenge.
A well-run investigation balances thorough fact-finding with legal safeguards, cost control, and risk management. The procedures chosen must align with the nature of the allegations, the size of the organization, and the likelihood of regulatory or litigation exposure.
Preserving Attorney-Client Privilege During an Investigation
One of the most critical considerations in conducting an internal investigation is protecting attorney-client privilege and attorney work product.
Communications between employees and company counsel are privileged when made for the purpose of securing legal advice for the corporation. Importantly:
- The privilege belongs to the company—not the employee
- Employees must be given proper Upjohn warnings
- Counsel must clearly explain that they represent the company
Failure to provide appropriate warnings can result in privilege disputes, disqualification issues, or ethical exposure.
Investigations conducted pursuant to compliance programs or corporate policy can still be privileged if a significant purpose is to obtain legal advice.
Document Review: The Foundation of Every Corporate Investigation
Document review is where most investigations begin—and where critical evidence is often found.
Corporate documents frequently provide the roadmap for witness interviews, timelines, and key decision points. These may include:
- Governance documents (bylaws, board minutes, SEC filings)
- Prior litigation or regulatory productions
- Outside counsel and auditor files
- Employee emails and messaging platforms
- Contracts, invoices, receipts, and accounting records
- Organizational charts, compliance manuals, personnel files
In many investigations, the “hot document”—an email, memo, or ledger entry that clarifies misconduct—emerges during careful document review.
Implementing a Litigation Hold and Preserving Evidence
If litigation or regulatory action is anticipated, immediate preservation steps are required.
Counsel should:
- Issue a document preservation notice (litigation hold)
- Suspend automatic email deletion systems
- Work with IT to preserve metadata and chain of custody
- Maintain logs of all preservation steps taken
Failure to properly preserve electronic data can result in sanctions, adverse inferences, or regulatory penalties.
Reviewing Employee Files and Electronic Communications
Employee-maintained files often contain key evidence.
These may include:
- Emails and messaging apps
- Handwritten notes
- Calendars and phone logs
- Expense reports and receipts
Counsel—not employees—should determine the parameters of email searches, often using eDiscovery vendors. Allowing employees to self-select responsive documents creates risk.
In certain cases, it may be necessary to review files without advance notice to prevent destruction or retaliation. However, privacy laws and reasonable expectations of privacy must be considered, especially for personal devices or files marked “personal.”
Clear company policies stating that workplace communications may be reviewed significantly reduce privacy challenges.
Electronic Document Review (EDR) and eDiscovery Best Practices
Modern investigations routinely involve large volumes of electronic data.
Electronic Document Review (EDR) allows counsel to:
- Search by keyword, metadata, and date ranges
- Use predictive coding and clustering tools
- Identify near-duplicates efficiently
- Preserve metadata and chain of custody
Secure access controls are essential to protect sensitive information such as personally identifiable information (PII), trade secrets, or health data.
Qualified personnel and defensible methodology are critical in the event the review process is later challenged.
Using Questionnaires in Corporate Investigations
In large organizations, questionnaires can efficiently gather information from a broad group of employees.
Benefits of Questionnaires
- Generate investigative leads
- Narrow or expand scope
- Collect information quickly and cost-effectively
Limitations
- No ability to assess demeanor
- Risk of misunderstanding questions
- No opportunity for immediate follow-up
Questionnaires are most effective in companies with hundreds of employees. In smaller organizations, direct interviews are often more efficient.
Responses should be returned to counsel—not management—and confidentiality warnings should be included.
Conducting Effective Employee Interviews
Interviews are central to fact development.
Best practices include:
- Conduct interviews in person or via video when possible
- Have two professionals present (one asking questions, one taking notes)
- Provide clear Upjohn warnings at the outset
- Explain that privilege belongs to the company
- Avoid audio recordings or court reporters in most cases
Employees may consult their own counsel. If a current employee refuses to cooperate without legal protection, termination may be appropriate, subject to whistleblower protections and employment laws.
Preparing and Protecting Interview Memoranda
Interview memoranda create a record of witness testimony but can present discovery risks.
To preserve work product protection:
- Avoid purely verbatim note-taking
- Incorporate attorney impressions and strategy
- Mark documents as privileged and confidential
- Avoid circulating drafts unnecessarily
Memoranda should be prepared promptly and reviewed for accuracy.
Using Private Investigators in Corporate Investigations
Private investigators may assist with:
- Background checks
- Asset tracing
- Public records searches
- Financial lifestyle analysis
To preserve privilege protections, investigators should be retained through counsel. Engagement letters should explicitly prohibit unlawful conduct and require compliance with all applicable laws.
Use of undercover agents in internal investigations is uncommon and raises ethical concerns. If undercover tactics appear necessary, involving law enforcement may be more appropriate.
Balancing Thoroughness, Efficiency, and Legal Risk
No two internal investigations are identical. The sequence of document review, questionnaires, interviews, and expert involvement depends on:
- Nature of the allegations
- Regulatory exposure
- Size of the organization
- Likelihood of litigation
A strategic approach ensures credibility while minimizing unnecessary cost and risk.
How Peters Brovner Conducts Defensible Internal Investigations
The way an internal investigation is conducted can determine regulatory exposure, litigation risk, and reputational impact. Early legal guidance is critical. Peters Brovner helps organizations structure and execute investigations that withstand scrutiny and protect privilege.